Angioscopy, a type of endoscopy, is a procedure used to explore vessels. When angioscopy is used to observe the inside of blood vessels, the visual field appears as a solid red. In older times, prototype angioscopy has been used for coronary arteries in the United States. At that time, an occlusion-type angioscopy was used. It was potentially dangerous for coronary arteries because the coronary arteries were occluded during an observation by angioscopy. In Japan, non-obstructing -type angioscopy (NOA) has been developed. The primary approach in NOA involved visualizing the field by injecting low-molecular-weighed dextran into the area between the 4-Fr probing catheter and the fiber. This diluted the blood and expanded the field of view.
NOA clarified the mechanisms of coronary plaque rupture [1], distribution [2], stabilization by drugs [3], and neointimal coverage and restenosis of stents. [4] We further developed a dual infusion method to widen the visual field, utilizing infusions from probing and 6-Fr guiding catheters. [5] Using the method, angioscopy has become easy, and the application has expanded to any type of vessel, such as the aorta. [6] We named the system a non-obstructing -type general angioscopy (NOGA)
Generally, the plaques and injuries of the aorta are evaluated by computed tomography, magnetic resonance, and transesophageal echocardiography. However, the world observed through NOGA was entirely different from what had been seen with previous imaging modalities or pathology. [7] The traditional modalities show still images and have poorer spatial and temporal resolution compared to NOGA. NOGA demonstrated vivid images of spontaneously ruptured aortic plaques (SRAPs). SRAPs were also found in 80.9 % of patients with or suspected coronary artery disease.
In the debris from scattered plaques such as puff-chandelier plaques, which reflected against the light of the angioscopic fiber and scattered like puff, cholesterol crystals (CCs) were found. However, empty clefts in samples with Hematoxylin-eosin stain were treated as CCs. There are lots of kinds of crystals in our body. We successfully demonstrated CCs as real imaging by soft preparations with polarized light microscopy. [7] CCs are spotlighted in the field of innate inflammation during atherosclerosis and plaque rupture. We demonstrated CCs were recognized and engulfed by macrophages, NLRP3 inflammasome was activated, and the inflammatory cytokines were provoked. [8]
The asymptomatic embolization of aortic debris, including CCs, may be related to acute and chronic organ damage such as stroke, dementia, frail, and sarcopenia. [9] In ischemic stroke, SRAPs are distributed in the proximal aorta, such as the aortic arch [10], and SRAPs may cause stroke more than thought because CCs are detected from “thrombectomy” samples. [11]
NOGA applications have been expanded to guide stent graft implantation. Good results were reported covering the fissures detected by NOGA. [12] Moreover, NOGA is also applied to evaluate the intervention for structured heart disease. We believe aortic dissection will be overcome by the observation with NOGA! The new world will come with the upcoming new type of angioscopy!